What is the best way to send mail from different domains through one SMTP?

Question

Email

Actually there is a CRM in which mail can be collected from different mail servers and different domains .
But sending occurs through msmtpd, which is just authorization on one of the accounts.
And everything works until the mailboxes are on the same domain.
But naturally, when sending a letter from a "foreign" domain, this domain is in the from field, and the SMTP server honestly sends it to the forest.
Accordingly, what is the best way to resolve this issue?
As far as I understand, you need to raise the daemon by mail and configure it so that, having already understood this letter inside itself (we can’t edit the CRM) , it already figured
out from which server to send the letter further.
Actually, you need the simplest option.
The OS doesn't matter.

Answer 1

Try like amazon ses or sendpulse.

Answer 2

Requires an explanation of what it means from "alien". Not belonging to you? So this is pure spam, even if you set up any MTA - such letters will most likely turn into a pumpkin.
You can try to spoof, use your own domain in the envelope part, and fake in the from part, but the delivery rate will also be doubtful and will depend heavily on the correct configuration of the Email DNS Security part (spf/dkim/dmarc).